33 2 Wager. — On the Structure and 
antheridium pass over into the oosphere ; and if there is 
more than one antheridium, they all usually, but not always, 
empty their gonoplasm one after another into the oosphere. 
Marshall Ward also (’83), in a very careful description of 
the process of fertilization in various species of Pythium , 
points out that £ the contents of the oogonium contract away 
from the wall towards the centre, strings and bands of proto- 
plasm being left attached to the inner wall.’ At a later 
stage, the central mass becomes rounded off, leaving a small 
quantity of protoplasm between it and the wall of the 
oogonium, the periplasm. This appears to be much smaller 
in amount than that found in Peronospora or Cystopus. The 
protoplasm of the antheridium, which contains a number of 
brightly refractive granules, sends out a fertilizing tube, which 
comes in contact with the oosphere or egg-cell. The contents 
of the antheridium then pass over almost entirely into the 
oosphere, a very small quantity only being left in the anthe- 
ridium. A thin skin appears round the oospore and ultimately 
a thick envelope which is derived from the periplasm. 
In Phytophthora again De Bary (’84) points out that the 
process of oospore formation is much the same as in Pythium, 
except that only a very small quantity of protoplasm passes 
over into the oosphere through the fertilization tube, and this 
portion is not distinctly separated beforehand. In Perono- 
spora and Cystopus the passage of protoplasm could not be 
seen (’63—84). 
Neither Fisch (’85) nor Chmielewsky (’89) appear to have 
clearly observed the process of fertilization in Cystopus , and 
Fisch is not quite clear as to fertilization in Pythium. 
It would of course be useless to offer at the present time 
any extended generalization from a comparison of the mode 
of fertilization of Cystopus as described in this paper with 
those methods described by earlier observers on other 
members of the Peronosporeae, as the latter are obviously 
incomplete ; but it may be useful to point out that my 
observations on Cystopus are so far in general agreement 
with the observations on Phytophthora described by De Bary, 
